Manufacture of thermoplastic shoe stiffener material and shoe stiffener blanks



June 12, 1934. 1,962,603

. S. LOVELL MANUFACTURE OF T MOPLASTIC -s STIFFENER MATERIAL SHOE STIFFENE LANKS ed Dec. 4, 1951 Patenterl June 12, 1934 PATENT OFFICE MANUFACTURE OF THERMOPLASTIC SHOE STIFFENER MATERIAL AND SHOE STIFF- ENER BLANKS Stanley P. Lovell, Newton, Mass., assignor to Beckwith Manufacturing Company, Boston, Mesa, a corporation of Massachusetts Application December 4,1931, Serial No. 578,921

9 Claims.

This, invention relates to the manufacture of shoe stifiener material and shoe stiffener blanks more particularly of the thermoplastic variety, comprising a flexible fibrous. web of a bibulous character as the foundation material associated with a thermoplastic stiffening composition either as a surface layer and/or as an impregnant in the interior of the foundation. Such thermoplastic stiffening compositions impart to the shoe stiflm ener material or the shoe stiffener blanks cut therefrom the properties of softenability and mouldability under the application of moderate temperature below that injurious to leather, wherefore the heat-softened blanks can be moulded to the desired shape in place in the shoe upper and then permitted to set and stifien. in such shape.

One of the objectionable characteristics of most thermoplastic stiffening compositions, especially those in current use, on account of their low cost and their highly eifective stifiening quality, is that they are friable or brittle, and consequently impart the property of inflexibility at normal temperatures to the fibrous web used as the carrier sheet or foundation material. For example, thermoplastic stiffening compositions. containing rosin have this fault, even when blended withv a certain amount of other thermoplastic stiffening agents, such as asphalt. Consequently, even when associated with a flexible fibrous web, the resulting sheet does not lend itself to accumulation as a roll at normal temperatures without serious cracking of the continuous phase of stiffening composition. This cracking or breaking of the sheet constitutes a permanent injury, inasmuch as the cracks are not repaired when blanks cut fromthe sheet are heat-conditioned for assembly with the shoes. Even when the sheet, rather than being accumulated as a roll, is cut into short lengths for storing, shipping, and dieing-out into shoe stiifener blanks, cracks are usually developed in the areas of the sheet immediately outside the lines of cutting of the dies.' This gives rise to the necessity of placing the dies sumciently apart longitudinally of the sheet to avoid cracks emanating from one row of blanks to the next succeeding row of planks to be cutby the same series or'gang of dies transversely of the sheet. This 'sort of practice entails the loss of considerable sheet material.

In accordance with the present invention, I associate the friable thermoplastic stiifening composition in a molten state with a continuous,

flexible fibrous web so as to lead to a continuous phase of the composition, but rather than allowing the resulting sheet to cool to room temperature as ordinarily, I cool it sufiiciently only to congeal the composition and thereby to avoid exudation from the sheet. If the cooling of the sheet is thus arrested at a temperature considerably above room temperature, the sheet remains sufficiently pliant to be flexible over a wide angle without cracking or disrupting the continuity of the phase of thermoplastic composition. This is attributable to the fact that although liquidity in the thermoplastic stiffening agent is destroyed, nevertheless the sheet can be kept at a sufliciently high temperature consonant with a wide angle of flexibility in the continuous phase Z0 of thermoplastic agent and the flexible foundation with which it is combined. My invention, therefore, involves first associating the molten thermoplastic stiffening agent with a continuous flexible fibrous web, and then imparting to the resulting sheet a temperature whereat there is no exudation of the agent from the sheet and whereat the sheet can advantageously be cut progressively into shoe stiffener blanks or accumulated as a roll, with no danger of damaging the sheet through cracking. As a roll, the sheet can be best stored or shipped to the shoe manufacturer for cutting into shoe stiifener blanks. The roll should not, however, .be unwound with the sheet at normal temperature conditions, as the sheet becomes set in its convoluted form and 1 cracks badly in being unwound. In accordance with the present invention, the sheet being unwound from the roll is heated short of the temperature at which it oozes, but sufliciently high to become pliant, whereupon it is progressively cut into shoe stiffener blanks in such heated state. The heat may be applied to the roll as a whole in a closed chamber, or may be applied locally as by directing a blast of steam or other heated medium into the angular space formed between the roll and the sheet, as the latter parts tangentially from the roll.

With the foregoing and other features and obiects in view, my'invention will now be described in conjunction with the accompanying drawing,

wherein a Figure 1 represents more or less diagrammatically and conventionally one form of aparatus for treating a continuous web of fibrous material with a thermoplastic stiifening agent and accumulating the resulting sheet as a roll.

Figure 2 is a similar representation of apparatus for unwinding a plurality of rolls simultane- 110 ously and for cutting the several sheets into shoe stiffener blanks.

Figure 3 is a plan view of a fragment of the sheet and illustrates the manner of cutting box toe blanks therefrom.

As shown in. Figure 1, I can start with a roll 1 of a suitable fibrous web 2, such as wool felt, cotton flannel, or a waterlaid web of fibers fabricated on papermaking machinery. The web 2 can be progressively unwound from the roll and led through a bath 3 of any suitable molten thermoplastic stiffening composition, for instance, one made up of about 50% rosin and about 50% bitumen having a melting point of about 200 to 250 13. (ball and ring test) as a uniform liquid. blend or mixture. A number of guide rolls a are shown placed at suitable locations for guiding the web into and out of the bath and past the other instrumentalities employed. The bath is preferably at a temperature of about 320 to 350 F., as at such temperature the heat-liquefied composition has sufficient fluidity to penetrate quickly and uniformly throughout the web. The impregnated sheet is then cooled to congeal the composition therein, but cooling should be arrested at atemperature conducive to the desired quality of pliancy in the sheet. Using the specific mixed impregnant described, the' impregnated sheet is preferably cooled to a temperature of about 150 to 212 15. As shown, the cooling can be accomplished by bringing a face of the sheet into contact with one or more cooling drums 5, through which cold water or other suitable cooling medium may be circulated. The drums 5 are preferably caused to rotate in baths of water 6, which prevents sticking of the sheet to the drums. Any other suitable cooling means may be employed to reduce the temperature of either or both faces of the sheet to the desired degree. The partially cooled sheet is now in a condition to be accumulated as a roll 7, shown resting on a pair of supporting mandrels 8. If it is desired to provide positively against sticking of the successive convolutions in the roll 7, a suitable powder, like talc dust, can be applied to one face of the sheet before it is accumulated as from a distributing box 9. The dusting of the sheet is not, however, an essential step, as there is no tendency for tenacious sticking between the successive convolutions in the roll 7 and thereby to lose their essentially individualized and separable character. The roll 7 constitutes a convenient package for storing, handling, and economically shipping the sheet material. of cracking the sheet material when stored, handled, or shipped in this form.

When the sheet material is to be unwound from. the roll for cutting into shoe stiffener blanks, it should be conditioned by heat for such unwinding and cut as already described. The cutting is preferably accomplished as customarily by means of gang dies designed to operate upon a plurality of superposed sheets at a time. This kind of practice is accordingly illustrated in Figure 2, wherein a plurality of rolls, specifically six rolls, of the sheet material are shown mounted for unwinding on arbors 10 forming part of a horse or frame 11. The'arbors 10 can all be rotated by a common chain 12 engaging sprockets l3 fixed at their ends. The motive power for the chain can be supplied from a sprocket 1d fixed on a shaft 15 which derives its motion from. a hand-wheel or other suitable means (not shown). Before being unwound from the rolls and superposed, the sheets coming from the va- T'nere is little liability neeaeoe rious rolls can be suitably heated while still in roll form, by enveloping the rolls in an atmosphere of hot air or steam. As shown, the frame 11 is housed within a chamber'lfi halving steam pipes 17 near its bottom. The rolls can be kept in the chamber until the sheet material has acquired the appropriate elevated temperature and pliancy substantially throughout, whereupon the ar'bors 10 are caused to rotate and the sheets coming from the various rolls can be caused to converge toward the exit opening 18 of the chamber and then brought into superposed contactual relationship in the nip of a pair of rolls 19 arranged outside of the opening 18. The superposed sheets can then be led progressively, as desired, into a press 20 provided with one or more transverse rows of gang dies, which operate on successive portions of the sheets to cut out shoe stiffener blanks, for instance the box toe blanks 21 shown in Figure 3. Inasmuch as the sheets are pliable while they are being out, there is no danger of their cracking. This means that the dies can be closely spaced to cut the sheets with minimum scrappage, as illustrated in Figure 3.

As already indicated, there are instances where the continuous sheet need not be accumulated in roll form as a package for storage and shipment, but may be out directly into shoe stiffener blanks by the shoe stifiener manufac turer immediately after impregnation and partial cooling of the sheet. If the continuous sheet I is exposed to room temperature for too long a period of time so that it loses its desired pliancy before reaching the dieing-out or cutting mechanism, provision should be made to reheat the sheet to restore the desired condition of pliancy thereto for the dieing-out or cutting operation. Irrespective of whether the blanks are cut out at the shoe stiffener factory at the same time that the shoe stiffener material is being made, or whether the sheet material is first accumulated into a roll, my invention involves keeping a continuous sheet in the desired pliant condition during the cutting or dieing-out operation, in consequence of which there is much less waste, because the cutting dies can be placed as closely as possible on successive portions of the sheet and because there are only two terminal edges in a sheet of indefinite length whereat material can be lost, as against the large number of such edges in the short length sheets heretofore used.

I claim:

1. In a method of fabricating shoe stifieners, those steps which comprise associating a normally solid and friable thermoplastic stiffening agent as a continuous phase with a continuous, flexible fibrous web, controlling the temperature to a point at which the stiffening agent does not exude from the sheet and sufiiciently high to keep said sheet pliant and said face continuous, and convoluting the resulting sheet into a roll under such conditions and thereby also keeping the convolutions in an essentially individualized and separable condition.

2. In a method of fabricating shoe stiifeners, those steps which comprise impregnating a continuous, fiexible fibrous web with a normally solid and friable thermoplastic stifiening agent in a molten state, cooling the resulting impregnated sheet below the congealing temperature of said agent but short of destroying its pliancy, and convoluting the sheet so cooled into roll form, thereby keeping the convolutions in an essentially individualized and separable condition.

3. In a method of fabricating shoe stiffeners, those steps which comprise impregnating a continuous, flexible fibrous web with a molten rosin composition at above the melting point of said composition, and convoluting the resulting sheet into a roll at a temperature of about 150 to 212 F., thereby keeping the convolutions in an essentially individualized and separable condition.

4. In a method of fabricating shoe stiflener blanks from a continuous sheet associated with a rosin composition rendering said sheet normally inflexible, those steps which comprise imparting tosaid sheet a temperature of about-150 to. 212 F., and progressively cutting out closely spaced blanks from said sheet while at such temperature.

5. In a method of fabricating shoe stiffener blanks from an accumulation of convoluted sheet shoe stiffener material carrying a normally solid and friable thermoplastic stifiening agent rendering said sheetnormally inflexible, those steps which comprise progressively removing said sheet from said accumulation while, it is heated to a temperature imparting pliancy thereto but below the melting-point of said agent, and progressively cutting out closely spaced blanks from said sheet while it is so heated.

6. In a method of fabricating shoe stiffener blanks from an accumulation of convoluted fibrous sheet material impregnated with a rosin composition rendering said sheet normally inflexible, those steps which comprise progressively removing said sheet from said accumulation while it is heated to a temperature of about 150 to 212 F., and progressively cutting out closely spaced blanks from said sheet while it is so heated.

- '7. In a method of fabricating shoe stiffener blanks from a sheet associated with a normally solid and friable thermoplastic stiffening agent rendering said sheet normally inflexible, that step which comprises bringing the sheet to a condition under which closely spaced dies may operate to punch out clean blanks free from cracks or tears,-by controlling the temperature of the sheet to a point at which the stiffening agent does not exude from the sheet .and below the congealing temperature of the stiffening agent and at which the sheet is pliant, and cutting out closely spaced blanks from said sheet.

8. In a method of fabricating'shoe stiffener blanks from a sheet associated with a normally solid and friable thermoplastic stiffening agent rendering said sheet normally inflexible, that step which comprises bringing the sheet to acondition under which closely spaced dies may operate to punch out clean blanks free from cracks or tears, by controlling the temperature of the sheet within substantially 150 F. to 212 F. at which the stiffening agent does not exude from the sheet and below the congealing temperature of the stiffening agent and at which the sheetis pliant, and cutting out closely spaced blanks from said sheet.

9. In a method of manufacturing shoe stiffeners from sheet material comprising a normally solid and friable thermoplastic stiffening agent as a continuous phase with a continuous web which comprises removing the sheet material from a roll in a condition under which closely space dies may operate to punch out clean blanks free from cracks or tears, by controlling the temperature of the sheet material to a point at which the stiffening agent does not exude from the sheet and'below the congealing temperature of the stiffening agent and at which the sheet is pliant, and cutting out closely spaced blanks from said sheet.

STANLEY P. LOVELL. 

